The object of this project is to understand the mechanism of RNA transcriptional control in eukaryotes. To this end we have developed a system for studying RNA transcription in vitro using chromatin as template. Using an assay for measuring RNA polymerase initiation sites we have shown that histones alone can account for the restriction of RNA synthesis on chromatin and in particular fl plays an important role in this process. Propagation of RNA polymerase is also restricted by chromatin proteins. Although RNA polymerase requires DNA unwinding for its activity, the slower rate of propagation on chromatin is not due to inhibition of DNA unwinding by chromatin proteins. Finally we are probing the structure of chromatin using DNA methylase to selectively label regions of chromatin not covered by proteins. With this technique we can demonstrate that exchange of chromatin proteins does not take place to any large extent during the preparation of chromatin. BIBLIOGRAPHIC REFERENES: Cedar, H. (1975) Transcription of DNA and Chromatin with Calf Thymus RNA polymerase B in vitro. J. Mol. Biol. 95, 257-269.